RPMs fluctuate at cold start/sputter on mid-acceleration
#1
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Year: 1994
Model: Cherokee(XJ)
Engine: 4.0 "high output"
RPMs fluctuate at cold start/sputter on mid-acceleration
I have a 1994 Jeep Cherokee Sport 2WD with the 4.0 engine. Recently it's developed a new issue, it started after I disconnected the front thermostat temp sensor because I was having overheating issues and my temporary solution was to have the accessory fan run at all times. Now when I start the jeep after it's been siting for a few hours the RPMs rise and dip, rise and dip for about 30 seconds-1 minute. If I attempt to drive it when it's doing this it'll sputter really aggressively, it hasn't stalled but it jerks. I also have an issue that maybe playing into it, If I'm cruising along it's fine but if I hold the throttle in about the half way position it'll sputter and the RPMs will jump up and down really aggressively, before it use to be only at half throttle and now at half throttle and WOT it sputters, I checked the codes and it's throwing camshaft position sensor pops and some other codes that I know I'm misreading. could it be the CPS or does anyone else have this issue.
P.S. I also have a bad motor and transmission mount (I swear I'm going to fix it soon, I just keep forgetting every time I go to a local Pull-A-Part).
P.S. I also have a bad motor and transmission mount (I swear I'm going to fix it soon, I just keep forgetting every time I go to a local Pull-A-Part).
#2
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Year: 1988
Model: Cherokee
Engine: 4.0
Note from DJ
My guess on your problem is because you have disconnected the engine water temperature gage that the Power Control Module needs information from when establishing the correct fuel trim.
Then your O2 sensor is telling the Power Control Module I’m reviving the wrong exhaust air mixture so change the fuel trim.
Now the Power Control Module is obsoleting the fuel trim numbers back and forth trying to make every happy.
My guess on your problem is because you have disconnected the engine water temperature gage that the Power Control Module needs information from when establishing the correct fuel trim.
Then your O2 sensor is telling the Power Control Module I’m reviving the wrong exhaust air mixture so change the fuel trim.
Now the Power Control Module is obsoleting the fuel trim numbers back and forth trying to make every happy.
#3
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Year: 1998 Classic (I'll get it running soon....) and 02 Grand
Model: Cherokee (XJ)
Engine: 4.0
Yup. The PCM needs the correct data.
On the other hand, if you have been overheating, it's likely your CPS has died. They don't like getting too hot. It's a Cherokee Thing. CPS should ONLY be NGK or Mopar - the track record with aftermarket sensors is not good at all.
Might help to post the codes you are seeing.
If you need to have your fan running all the time as a temporary workaround until you can fix things properly, you can always install a manual switch for it. It doesn't take very long.
On the other hand, if you have been overheating, it's likely your CPS has died. They don't like getting too hot. It's a Cherokee Thing. CPS should ONLY be NGK or Mopar - the track record with aftermarket sensors is not good at all.
Might help to post the codes you are seeing.
If you need to have your fan running all the time as a temporary workaround until you can fix things properly, you can always install a manual switch for it. It doesn't take very long.
#4
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Year: 1994
Model: Cherokee(XJ)
Engine: 4.0 "high output"
The jumping RPMs is new where the sputtering and jerking during mid acceleration have been there since I got the jeep in February but the WOT jumping is new, I just wanted to clarify, I'll look into manually wiring the accessory fan as well as possibly swapping the mechanical for electrical since I have one of those ebay slim fans laying in my garage from my old 1500 truck.
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